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The eutectic Sn-Zn-Al solder alloy was used [composition: 91Sn-9(5Al-Zn)] to investigate the intermetallic compounds (IMCs) formed between solder and a Cu substrate. Scanning electron microscope, transmission electron microscope, and electron diffraction analysis were used to study the IMCs between solder and a Cu substrate. The ␥-Cu 5 Zn 8 and ␥Ј-Cu 9 Al 4 IMCs were found at the Sn-Zn-Al/Cu interface. Thermodynamic calculation can explain the formation of ␥-Cu 5 Zn 8 and ␥Ј-Cu 9 Al 4 IMCs instead of Cu-Sn compounds. The formation and growth of ␥Ј-Cu 9 Al 4 IMC at 423 K resulted in the decrease of adhesion strength at the interface of solder and a Cu substrate, where the Kirkendall voids were severely formed. As the heating time increased up to 1000 h at 423 K, the adhesion strength between the eutectic Sn-Zn-Al solder and a Cu substrate decreased from 7.6 ± 0.7 MPa to 4.4 ± 0.8 MPa.

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Transformation kinetics of mullite formation in kaolin–Al2O3 ceramics was studied by x-ray diffraction, transmission electron microscopy, and energy dispersion spectrometry. The mullitization process of kaolin–Al2O3 ceramics is described by two stages; one is the primary mullite transformation at 1273 to 1573 K, and the other is the secondary mullite formation at 1573 to 1873 K. The activation energy of 1164.6 kJ mol-1 obtained for the secondary mullite formation is lower than 1356.9 kJ mol-1 for the primary mullite transformation by the general form of the Johnson–Mehl–Avrami equation. The lower value of growth morphology parameter strongly supports that in the secondary mullite formation the added alumina is dissolved into glassy phase and the mullite is then precipitated.